This invention relates to engines and engine propelled vehicles and particularly to relatively small multi-cylinder engines such as those commonly used in personal watercraft such as jet skis and jet boats. It is envisaged that the invention is equally applicable to other xe2x80x9cpersonal-typexe2x80x9d small engined vehicles such as snow-mobiles and small all-terrain vehicles.
As a result of the increasing concern in regard to air pollution by exhaust gases from internal combustion engines, legislation is beginning to be introduced or made more stringent in some countries relating to the level of emissions contained in exhaust gases from the engines of a range of relatively small vehicles. This is in addition to the existing legislation relating to the emissions from cars and trucks and like large vehicles.
Further, having regard to the size and weight of the engine of small vehicles, it is important to design such engines so as to occupy the smallest possible space within the vehicle and, as a consequence, reduce the overall size and weight of the vehicle. At the same time, such engines must be able to develop a relatively high power output in order to obtain a level of performance acceptable to the purchasing public.
In order to achieve relatively high power outputs together with low exhaust emissions, it has in some cases been necessary to avoid the use of the more conventional carburettor or manifold injected engines and to adopt a direct injected engine in order to achieve these desired high power outputs and low exhaust emissions. However, such engines typically require additional componentry which can result in an increase in the space requirement of the engine within the vehicle and thus it is important to obtain an engine layout which is relatively compact.
It is therefore the object of the present invention to provide an engine particularly suitable for use in small vehicles including personal watercraft which is of minimum physical dimensions and an acceptable manufacturing cost.
With this object in view there is provided, according to one aspect of the invention, an in-line multi-cylinder internal combustion engine having on one side of the cylinder block an air induction system and on the opposite side an exhaust system, each extending generally in the direction of the length of the engine and both said systems extending beyond the plane of a cylinder head of the engine, a fuel rail extending in the direction of the length of the engine and mounted on the cylinder head to be located between the air induction system and said exhaust system, said fuel rail overlying and being in fuel transfer communication with respective fuel injection units located in the cylinder head, and each said fuel injector communicating with a respective cylinder of the engine.
Preferably, a spark plug is mounted in each cylinder to enter the cylinder at a level below the top of the fuel rail and to project from the cylinder head to one side of the fuel rail. The spark plugs may be arranged in the cylinder head at a location between the engine exhaust system and the fuel rail. Conveniently, the fuel rail is configured so as to provide sufficient clearance on the exhaust system side thereof, when mounted on the cylinder head, to enable the spark plugs to be appropriately arranged within the cylinder head on the exhaust system side thereof. Alternatively, for different engine configurations, the fuel rail may be configured to allow for appropriate location of the spark plugs on the air inlet side of the engine.
Preferably, the fuel injector units are of the type wherein the fuel is entrained in a compressed gas for delivery to the engine, and the fuel rail includes both a passage for the conveyance of fuel and a further passage for the conveyance of the gas, normally air. Preferably, the fuel rail also has incorporated thereon a fuel pressure regulator and a gas pressure regulator. These regulators are conveniently mounted on the fuel rail on the side thereof remote from the spark plugs. More particularly, the regulators are arranged on the fuel rail at a location immediately adjacent the air induction system.
Conveniently, the fuel rail is configured such that when mounted on the cylinder head, the regulators mounted thereon are located adjacent the air induction system such that sufficient clearance is provided on the exhaust side of the cylinder head for the spark plugs to be arranged therein. In this regard, the air induction system may be able to be slightly angled so as to enable the appropriate location of the fuel rail on the cylinder head. Alternatively, for an alternative location of the spark plugs, the exhaust system may be able to be slightly angled for similar reasons.
Preferably, the fuel rail is arranged such that an air inlet thereto is located at an opposite side to a fuel inlet thereto. Conveniently, the air and fuel inlets are arranged at opposing ends of the length of the rail with the air inlet being located adjacent that end of the engine where a drive-shaft projects from the cylinder block. It is however to be noted that other arrangements for the location of the fuel and air inlets on the rail are possible such as, both at the same end on the length thereof. Preferably, the fuel inlet is arranged to correspond with that end of the engine adjacent which a fuel pump is located.
Preferably, the air induction system is configured to comprise one air flow control means for regulating the amount of air to each of the cylinders of the engine. Whilst it is possible to provide an individual air flow control means for each cylinder of the engine, each housed in an individual air conduit of the air induction system as is well known, for example, personal watercraft engines, the provision of a single air flow control means enables significant simplification of the air induction system. This in turn reduces the component cost thereof as well as contributing to a reduced overall size, weight and complexity of the engine.
Where the engine is of the type incorporating a fuel injector unit which delivers the fuel entrained in a gas to a combustion chamber of the respective cylinders, it is also necessary to provide an on-board source of compressed gas, typically air, for this purpose. The preferred source of compressed air is typically from an engine driven compressor. Conveniently, the compressor is driven by the engine via a portion of the engine crankshaft the projects from one end of the engine via a pulley or gear mounted thereon or on the drive-shaft coupled thereto, or by an appropriately provided surface of a coupling between the crankshaft and drive-shaft of the compressor. Accordingly, it is preferable to locate such a compressor on the engine such that it corresponds to an end of the engine wherein it is possible to conveniently couple the drive-shaft of the compressor to the engine crankshaft or a drive-shaft connected thereto. Some engines may have a camshaft to effect operation of the valves of the engine, and/or a balance shaft and the compressor may be suitably coupled to the camshaft or balance shaft to be driven thereby.
In an engine constructed so that a portion of the exhaust system projects beyond the upper extremity of the engine block at the end where the drive-shaft is located, and is adjacent an upper end of the engine block or the cylinder head thereof, it is preferable for the compressor to be mounted below the level of that portion of the exhaust system so that the compressor does not increase the overall size or length of the engine. Further, it is appropriate for the delivery port of the compressor to be located in the upper portion of the compressor when mounted so that the length of the conduit carrying the air to the fuel rail is minimised. That is, it is preferable to mount the compressor at that end of the engine which corresponds to the end where the drive-shaft thereof is located and also so as to correspond with the air inlet of the fuel rail. In this way, the length of the air line connecting the compressor delivery port and the air inlet to the rail is kept to a minimum.
This feature provides the advantage that the volume of the conduit to carry the air between the compressor delivery port and the nozzles of the fuel injector units, which is required to be pressurised prior to satisfactory operation of the fuel system, is kept to a minimum. Hence, whether this volume is xe2x80x9cpumped upxe2x80x9d by way of cylinder pressure during engine cranking such as is disclosed in the applicant""s U.S. Pat. No. 4,936,279 which is incorporated herein by reference, or whether xe2x80x9cpump upxe2x80x9d of this air volume occurs simply due to the first few cycles of the compressor, this desired location and arrangement of the compressor substantially reduces the overall xe2x80x9cpump upxe2x80x9d or pressurisation time of this air volume.
As previously described, for packaging reasons, the compressor may conveniently be arranged to lie beneath a portion of the exhaust system of the engine. That is, the compressor may conveniently be mounted adjacent the exhaust system to take advantage of any cavities or unused space created thereby so as to not contribute to an increase in the overall length, width or depth of the engine. It should however be noted that the compressor may similarly be mounted on the intake side of the engine and that similarly, such mounting may take advantage of any cavity created by the orientation and shape of the air induction system. Still further, the compressor may alternatively be located centrally of the drive-shaft end of the engine such that it is directly coupled thereto or directly driven thereof.
It should be noted that the feature of locating the compressor adjacent the exhaust system or induction system such that it does not contribute to an increase in the overall engine packaging size, and of locating the compressor to correspond with the drive-shaft end of the engine, is not limited to engines requiring a fuel rail to be mounted between the air induction and exhaust systems. Whilst such an arrangement of the compressor is particularly relevant to engines which do have a fuel rail mounted as such and which require a source of pressurised gas for operation, the arrangement is equally applicable to other configurations of fuel systems which may require a source of pressurised gas for operation.
Preferably, a fuel tank and fuel pump of the engine are located adjacent the end of the engine opposite to the location of the compressor with a fuel delivery line therefrom being connected to the adjacent end of the fuel rail. A fuel return line communicates the fuel pressure regulator thereon with the fuel tank. Preferably, the fuel pump is located within or immediately adjacent the fuel tank so that there is a minimum delay in delivery of fuel to the engine on initial start-up of the fuel pump. That is, the overall length of the fuel lines between the fuel tank and the fuel pump and also the length of the fuel lines between the fuel pump and the inlet to the fuel rail are kept to a minimum such that the priming time of these lines is minimal. In particular, the fuel pump suction line from the fuel tank is desired to be as short as possible so as to enable the fuel pump to supply fuel at a high pressure after as short a time as possible once the fuel pump begins operating.
As previously stated, it is convenient to locate the fuel pump such that the pump delivery aligns with the fuel inlet of the fuel rail. This obviously serves to minimise the length of the fuel line connecting these two components. This further contributes to a much neater and cheaper package due to the elimination of unnecessarily long fuel lines.
The location of the fuel pump adjacent or within the fuel tank also reduces the accumulation of fuel vapour in the fuel pump suction line prior to start up. This location also serves to keep the fuel pump away from the hot environment on or directly adjacent the engine such that satisfactory operation thereby is not compromised. A further benefit may also ensue from locating the fuel pump within the fuel tank in that the fuel tank and the fuel therein, within which the fuel pump operates, will operate as a sound insulator. That is, the noise generated by the fuel pump during operation, so far as the rider is concerned, will typically be reduced.
It should be noted that whilst the feature of locating the fuel pump adjacent or within the fuel tank is particularly applicable to the arrangement described wherein a fuel rail is disposed between the exhaust and air induction systems of an engine, the feature is equally applicable to other engine arrangements for personal watercraft and small engined vehicles which simply require a source of high pressure fuel for operation.
The fuel priming advantages as mentioned above are particularly important in respect of engine installations in personal watercraft such as xe2x80x9cjet skisxe2x80x9d which typically incorporate an engine cut-out that is activated if a rider is dislodged from or falls off the water craft. However, it is also important for the engine to be quickly started once the rider re-mounts and cancels the cut-out. The need for a quick start arises from the limited stability of some water craft, such as the jet ski when not being driven by the engine. These are important safety features in that the water craft is not left to operate without a driver aboard with the potential to injury other people in the water. Also the dislodged driver can be at risk of injury by the watercraft from which has been dislodged.
In one example the engine cut-out is connected to the driver by a lanyard so that if the driver is dislodged from the craft the separation of the driver from the craft cause the lanyard to activate the engine cut-out and hence stop the water craft. The cut-out of the engine can be achieved by interruption of either fuel and/or electrical energy to the engine to thereby terminate operation of the engine of the craft. The quicker response is achieved by interruption of the electrical energy supply.
Advantageously, in accordance with another aspect of the invention, the fuel system is activated on insertion of the lanyard cut-out. Thus the fuel supply is activated in advance of commencement of the cranking of the engine thus providing a more rapid engine start-up when cranked.
In alternative forms of the invention, following engine shut-down the fuel system may be activated prior to starting of the engine by any means indicating that the engine is about to be started. For example, a sensor may be provided which senses whether an operator is positioned in the driver""s seat of a vehicle. If so, the fuel system is activated, thus priming the fuel lines in preparation for engine start-up. Other indicators that the vehicle is about to be started may include movement of brake/accelerator/clutch devices, opening of a vehicle door, and insertion of a key into the vehicle ignition device.
The early activation of the fuel pump will result in the fuel pump being cycled for a short period of time to prime the fuel lines to the fuel rail prior to the rider activating the engine starter. As is well known, and common to most personal watercraft such as jet skis, one end of the lanyard is worn by the rider such that if the rider is dislodged from the jet ski, the other end of the lanyard will be disconnected from the jet ski and typically cause the engine to cut-out. Hence, by cycling the fuel pump as soon as the rider re-connects the lanyard, the fuel system is pre-primed such that upon activating the engine starter, the engine operation is established more quickly.
The invention will now be described with reference to the accompanying drawings in which there is illustrated one practical arrangement of an engine installation and layout incorporated in a jet ski.